henrike@webrtc.org | 0e118e7 | 2013-07-10 00:45:36 +0000 | [diff] [blame] | 1 | /* |
| 2 | * libjingle |
| 3 | * Copyright 2004--2005, Google Inc. |
| 4 | * |
| 5 | * Redistribution and use in source and binary forms, with or without |
| 6 | * modification, are permitted provided that the following conditions are met: |
| 7 | * |
| 8 | * 1. Redistributions of source code must retain the above copyright notice, |
| 9 | * this list of conditions and the following disclaimer. |
| 10 | * 2. Redistributions in binary form must reproduce the above copyright notice, |
| 11 | * this list of conditions and the following disclaimer in the documentation |
| 12 | * and/or other materials provided with the distribution. |
| 13 | * 3. The name of the author may not be used to endorse or promote products |
| 14 | * derived from this software without specific prior written permission. |
| 15 | * |
| 16 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED |
| 17 | * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF |
| 18 | * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO |
| 19 | * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| 20 | * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, |
| 21 | * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; |
| 22 | * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, |
| 23 | * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR |
| 24 | * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF |
| 25 | * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| 26 | */ |
| 27 | |
| 28 | /* |
| 29 | * linked_ptr - simple reference linked pointer |
| 30 | * (like reference counting, just using a linked list of the references |
| 31 | * instead of their count.) |
| 32 | * |
| 33 | * The implementation stores three pointers for every linked_ptr, but |
| 34 | * does not allocate anything on the free store. |
| 35 | */ |
| 36 | |
| 37 | #ifndef TALK_BASE_LINKED_PTR_H__ |
| 38 | #define TALK_BASE_LINKED_PTR_H__ |
| 39 | |
| 40 | namespace talk_base { |
| 41 | |
| 42 | /* For ANSI-challenged compilers, you may want to #define |
| 43 | * NO_MEMBER_TEMPLATES, explicit or mutable */ |
| 44 | #define NO_MEMBER_TEMPLATES |
| 45 | |
| 46 | template <class X> class linked_ptr |
| 47 | { |
| 48 | public: |
| 49 | |
| 50 | #ifndef NO_MEMBER_TEMPLATES |
| 51 | # define TEMPLATE_FUNCTION template <class Y> |
| 52 | TEMPLATE_FUNCTION friend class linked_ptr<Y>; |
| 53 | #else |
| 54 | # define TEMPLATE_FUNCTION |
| 55 | typedef X Y; |
| 56 | #endif |
| 57 | |
| 58 | typedef X element_type; |
| 59 | |
| 60 | explicit linked_ptr(X* p = 0) throw() |
| 61 | : itsPtr(p) {itsPrev = itsNext = this;} |
| 62 | ~linked_ptr() |
| 63 | {release();} |
| 64 | linked_ptr(const linked_ptr& r) throw() |
| 65 | {acquire(r);} |
| 66 | linked_ptr& operator=(const linked_ptr& r) |
| 67 | { |
| 68 | if (this != &r) { |
| 69 | release(); |
| 70 | acquire(r); |
| 71 | } |
| 72 | return *this; |
| 73 | } |
| 74 | |
| 75 | #ifndef NO_MEMBER_TEMPLATES |
| 76 | template <class Y> friend class linked_ptr<Y>; |
| 77 | template <class Y> linked_ptr(const linked_ptr<Y>& r) throw() |
| 78 | {acquire(r);} |
| 79 | template <class Y> linked_ptr& operator=(const linked_ptr<Y>& r) |
| 80 | { |
| 81 | if (this != &r) { |
| 82 | release(); |
| 83 | acquire(r); |
| 84 | } |
| 85 | return *this; |
| 86 | } |
| 87 | #endif // NO_MEMBER_TEMPLATES |
| 88 | |
| 89 | X& operator*() const throw() {return *itsPtr;} |
| 90 | X* operator->() const throw() {return itsPtr;} |
| 91 | X* get() const throw() {return itsPtr;} |
| 92 | bool unique() const throw() {return itsPrev ? itsPrev==this : true;} |
| 93 | |
| 94 | private: |
| 95 | X* itsPtr; |
| 96 | mutable const linked_ptr* itsPrev; |
| 97 | mutable const linked_ptr* itsNext; |
| 98 | |
| 99 | void acquire(const linked_ptr& r) throw() |
| 100 | { // insert this to the list |
| 101 | itsPtr = r.itsPtr; |
| 102 | itsNext = r.itsNext; |
| 103 | itsNext->itsPrev = this; |
| 104 | itsPrev = &r; |
| 105 | #ifndef mutable |
| 106 | r.itsNext = this; |
| 107 | #else // for ANSI-challenged compilers |
| 108 | (const_cast<linked_ptr<X>*>(&r))->itsNext = this; |
| 109 | #endif |
| 110 | } |
| 111 | |
| 112 | #ifndef NO_MEMBER_TEMPLATES |
| 113 | template <class Y> void acquire(const linked_ptr<Y>& r) throw() |
| 114 | { // insert this to the list |
| 115 | itsPtr = r.itsPtr; |
| 116 | itsNext = r.itsNext; |
| 117 | itsNext->itsPrev = this; |
| 118 | itsPrev = &r; |
| 119 | #ifndef mutable |
| 120 | r.itsNext = this; |
| 121 | #else // for ANSI-challenged compilers |
| 122 | (const_cast<linked_ptr<X>*>(&r))->itsNext = this; |
| 123 | #endif |
| 124 | } |
| 125 | #endif // NO_MEMBER_TEMPLATES |
| 126 | |
| 127 | void release() |
| 128 | { // erase this from the list, delete if unique |
| 129 | if (unique()) delete itsPtr; |
| 130 | else { |
| 131 | itsPrev->itsNext = itsNext; |
| 132 | itsNext->itsPrev = itsPrev; |
| 133 | itsPrev = itsNext = 0; |
| 134 | } |
| 135 | itsPtr = 0; |
| 136 | } |
| 137 | }; |
| 138 | |
| 139 | } // namespace talk_base |
| 140 | |
| 141 | #endif // TALK_BASE_LINKED_PTR_H__ |
| 142 | |